Tree or plant protection mat

ABSTRACT

One embodiment provides a modular green roof tray, house plant growth media and horticulture growth media, and a tree protection mat for weed and moisture control made from recycled disposable diapers. The growth medium and tree protection mat contain superabsorbent materials from diaper that can absorb waters and greatly reduce irrigation so to provide a drought resistant feature. One embodiment also provides a manufacturing process to perform 100% recycling of disposed diapers.

All or part of the subject matter described herein was carried out underNSF-SBIR Award 1046780. The government may have rights in the subjectmatter described herein.

BACKGROUND

Green roof systems are used on the roofs of buildings and provide anenvironment to host vegetation. A green roof system can offer energyconsumption reduction, sound insulation, food and flower production,reduction of greenhouse gas emission, preservation of habitat andbiodiversity, storm water retention, reduction in the urban heat islandeffect, and other benefits.

The main concerns for a green roof system include structural strength,managing or avoiding water leakage, and irrigation of roof plants. Abuilding with a green roof must be strong enough to support the growthmedium and the plants, especially after it is saturated with water.Waterproofing is a challenge as there may be a sustained water pressureon the roof in some systems. The aforementioned aspects are importantfor an intensive green roof, while irrigation is important for anextensive green roof. Current green roof technologies uses light weightgrowth medium to reduce the load on the infrastructure. For flat roofs,the main concerns are waterproof and structural design. For inclinedroofs, the growth medium immobilization and water retention need extraconsiderations. Pitched sheets or stair-like designs have been used forthis type of roof. The thinner growth medium layer of an extensive greenroof allows less water uptake and retention. In areas with infrequentprecipitation and/or high evaporation rates, irrigation may be requiredon a daily basis, which may offset the cost savings from a green roofsystem.

A similar situation requiring an environment to host vegetation existsin tree protection. Tree protection is important, especially for youngand newly planted trees, whose root system has not yet well developed.Most widely used method is mulching with wood chips that are recycledfrom green waste. This can preserve moisture, reduce competition fromweeds, and allow trees obtain essential nutrients to survive earlygrowth. But they are not very efficient and long-lasting and willdegrade quickly. Usually trees need to be remulched annually in spring.

One alternative solution for tree protection, especially for youngtrees, is to place weed mat around tree. These weed mats are usuallymade of plastic materials whose functions are just like mulch but lastlonger. Two different types of mats are available on the market rightnow: mats with and without pores. The major difference is that weed matwith pores allows rain water seep in while weed mat without porescannot. It seems weed mat with pores are more effective for waterpermeate through; however, it is less favorable for the customers in themarket. The argument preferring mat without pores is that the same poresthat allow water seep in can quickly evaporate out because of its highsurface area and small pore sizes. Both types of weed mats and woodchips' mulches rely primarily on the soil around trees for holdingmoisture. The mat or the mulch has no or very limited capability toabsorb water. Therefore the moisture content can vary in a wide rangedepends on the properties of soil and weather.

Meanwhile, hundreds of billions of dirty diapers are disposed annuallyas solid wastes and only a very small fraction of them are recycled.This is mainly due to the lack of technologies for efficient andcost-effective recycling. The valuable materials in these disposeddiapers could have found great applications if they can be properlyprocessed.

Disposable diapers are made of a variety of components. First, anabsorbent pad made of cellulose or cellulose acetate and superabsorbentpolymer (SAP) e.g., sodium polyacrylate is used to absorb body fluids.This pad is then placed into a tissue carrier, which can be made ofpolyester nonwoven fabrics or tissue paper. This tissue wrapped pad isthen sandwiched in between a layer of nonwoven fabric for interior and anon-permeable film for exterior. The nonwoven fabric includes of ahydrophilic layer to allow water to flow to the absorbent pad and ahydrophobic layer to keep the surface in contact with skin dry. Thenon-permeable film is made of polyethylene or cloth-like polyolefinfilms to prevent liquid leakage. To put all the above componentstogether, hot-melt adhesives are used. Elastomeric materials, suchpolyurethane, polyester or rubber are used in cuffs for both the waistand the leg to maintain tightness. Adhesive tapes or hook tapes are usedto provide mechanical grip for closure. Other components, such aslotions applied on the surface of top sheet, decorative film, wetnessindicator, and acquisition and distribution layers are very common indisposable diapers.

The complexity of the disposable diapers arises from the consumers' needfor a comfortable, effective, easy-to-use, and low-cost product.However, such a system has made traditional recycling impossible to doefficiently and cost-effectively with current technologies. As a result,most after-consumer disposable diapers end up as solid waste piling upin landfill fields. The lack of a product that can consume the recycledmaterials and proper purification technologies to produce high puritymaterials have played a great role in the landfill problem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Cross-section view of one embodiment of the modular green rooftray with snap-fit interlocking design. The components are 1, growthmedia; 2, cover; 3, tongue; 4, groove; 5, wall; 6, adhesive; 7, bottomlayer; and 8, tongue.

FIG. 2. Whole view of one embodiment of the modular green roof tray withsnap-fit interlocking design.

FIG. 3. Top view of one embodiment of the modular green roof tray withsnap-fit interlocking design.

FIG. 4. Two modular green roof trays connected together using oneembodiment of snap-fit interlocking design.

FIG. 5. Graphically presents the effects of SAP on the water losswithout nonwoven cover. The effects of SAP content on the water loss ofgrowth media without nonwoven cover. All the growth media were soakedfor at least 2 hours before free flowing water was removed. Then thecontainers for growth media was kept under constant artificial sun lightexposure till their weight is not changing over a period of 48 hours.

FIG. 6. Graphically presents the effects of SAP on the water loss withnonwoven cover. The effects of SAP content on the water loss of growthmedia with nonwoven cover. Growth media were soaked, and free water wereremoved before the nonwoven covers were added. The containers for thesegrowth media was exposed to the same conditions as those withoutnonwoven covers and weighted ever 24 hour till their weight stable overa period of 48 hours.

FIG. 7. One embodiment of a tree protection mat for weed control andmoisture conservation.

FIG. 8. Exhibit of vegetation establishment from seeds in growth mediawithout nonwoven cover (upper set of images) and with nonwoven cover(lower set of images). For the group without nonwoven cover, the grasswas sprouting and growing much less in the container with 100% SAPbecause of poor air permeability and poor root development. The sparselysprouted grasses in this container died after two weeks. The grasses inthe containers with 25% and 0% SAP initially sprout similarly with othertwo containers with 75% and 50% SAP. However, the growth of grasses inthe former two containers eventually became slow and died in four weeks.In contrast, the two containers with 75% and 50% SAP were able to keepthe grasses alive till 45th day with regular watering. After that, thegrasses survived another two weeks without watering. The total waterconsumption of each container is 3000 ml. For the group with nonwovencover, the sprouting and growth was similar except the total water usageis only 1800 ml for each container. Moreover, nonwoven cover did notinhibit sprouting and growth.

FIG. 9 Exhibit showing one embodiment of separation of diapercomponents. Pictures showing separation of diaper components using wetmethod, wetlay separation and mat formation processes. a, diapercomponents separated into two groups based on their densities:polyolefins float and SAP, pulp fibers and polyesters sink, b, matformation by wetlay process at USDA FPL, c, wet separation process: c1,agitation for mixing, c2 and c3, components settle down after agitationstopped, c4, lower layer is shown after upper layer decanted, d, upperlayer separation and drying, e, lower layer separation and drying.

FIG. 10. One embodiment of nonwoven mats that were prepared by wetlayprocess with or without refining procedure.

FIG. 11. Graphically shows total organic carbon of water samplescollected from water/SAP mixtures. Total organic carbon of water samplescollected from water/SAP mixtures under heat (50° C.) and ultravioletirradiation as well as the water sample collected after treatment. Tapwater was used as a control and shown as Time=0 months.

FIG. 12. Graphically shows the effect of WCMC mat on young tree growthafter 5 months.

FIG. 13. Exhibit shows an example of process flow diagram for the wetlayprocess.

FIG. 14. Presents a flowchart of one embodiment of production process ofweed control and moisture conservation mat from disposable diaper.

FIG. 15. Exhibit shows embodiments of panel and mat molded from recycleddiaper materials.

DETAILED DESCRIPTION OF THE SEVERAL EMBODIMENTS

One embodiment provides a light-weight, modular green roof tray withthree layer structure. The bottom layer (water-proof layer) of which ismade from recovered thermoplastic materials from recycling disposablediapers, the center layer of which is a drought resistant growth mediumcontaining superabsorbent polymers, and the top layer of which is aporous nonwoven cover. This design also depicts a novelthree-dimensional snap-fit locking mechanism. FIG. 1 illustrates thisgreen roof module design.

One embodiment provides a modular green roof tray with athree-dimensional snap-fit locking mechanism. This snap-fit interlockingmechanism can be combined with adhesives so that they can be permanentlyconnected to each other if such is desired. This design of snap-fitinterlocking mechanism is superior to conventional systems in which2-dimensional interlocking is used.

One embodiment provides a modular green roof tray with a cover using lowdensity and large pore-sized nonwoven mat. This cover performs as anenclosure of growth medium during the shipping and installation, allowsplants to grow through the pores, prolongs water retention time ofgrowth medium, and prevents erosion.

One embodiment provides a modular green roof tray with a cover using lowdensity and large pore-sized nonwoven mat. The water retention time withthis non-woven mat is 70% longer than that without the mat.

One embodiment provides a composition for drought resistant growthmedium in which the recovered and reinforced superabsorbent polymers(SAPs) from recycled disposable diapers is evenly mixed with soil thatcan be regular soil, peat moss, clay, expanded clay (commercial name asPerlite), or a mixture of them. SAP refers to the water absorbentmaterials recovered from diapers that include superabsorbent polymerparticles and cellulose fibers. The composition range of recovered andreinforced SAPs can be in between 10-90% of the total wet weight of thegrowth medium, which range includes all values and subrangestherebetween, including 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,70, 75, 80, 85, and 90% by weight, based on the total wet weight of thegrowth medium. In one embodiment, the composition is in between 40-75%of wet SAP weight.

One embodiment provides a composition for drought resistant growthmedium that the saturated growth media contained 20% more water contentbut 20% weight lighter compared other commercially growth media forgreen roof at a certain depth. Due to the drought resistant andlightweight feature of this new growth media, architecture design,vegetation selection and maintenance will be much more flexible. Suchgrowth media can be widely applied to different kinds of green roof:extensive, semi-intensive and intensive. It can provide more flexibilityto design a green roof for architectures to meet the load capacityrequirement. This kind of growth media is also applicable fornon-modular green roof design. Such growth media can be used for thegrowth of various plants (grass, sedum, flowering and tall plants). Itcan also be used for indoor house plants and other horticulture plants.Our growth media has been proven to be applicable for extreme conditionssuch as drought, high temperature, low temperature and highprecipitation.

One embodiment provides a young tree protection mat for weed control andmoisture conservation with three layers structure. The bottom layer(semi-permeable layer) is a porous nonwoven cover to hold the centerlayer in place; the center layer is a water absorbing pad containingsuperabsorbent polymers; and the top layer is a nonpermeable orsemipermeable panel or film made from recovered thermoplastic materialsfrom recycling disposable diapers or any other plastic materials. Thetop layer has funnel shaped dips with holes that allow collectionabsorption of rain water by the absorption pad.

One embodiment provides a recycling procedure to separate, recover andreinforce superabsorbent polymers from recycled disposable diapers.

One embodiment provides a recycling procedure to recover thermoplasticmaterials from disposable diapers. These thermoplastic materials includepolyolefins such as polyethylene and polypropylene, polyesters, andelastomers, etc.

One embodiment also provides a compounding procedure may be necessary tocreate high strength materials from the recycled thermoplastics andsmall quantity of cellulose materials due to insufficient separation.

One embodiment provides a new type of green roof module with noveldrought-resistant and lightweight growth medium developed from recycledsuper absorbent polymers from disposable diapers. In addition to thebenefits of regular green roof systems, this system offers a twentypercent increase in the amount of water absorbed and a twenty percentdecrease in total weight for a given depth of growth medium. This willprovide a much larger selection of plants and lower requirement forinfrastructure. While it allows more existing buildings suitable forgreen roof installation, it means lower building cost for newconstructions. In drought prone areas, the growth medium consumes lesswater at much lower frequency of watering. The presence of superabsorbent polymers in the growth medium may also have superiorstormwater management qualities due to water retention capability. Thegrowth medium can also help contribute towards Leadership in Energy &Environmental Design (LEED) certification in the materials & resourcescategory, especially the recycled content, regional materials, andrapidly renewable materials subcategories. Ordinary growth media used inthe current green roof market do not necessarily qualify for thesecategories. The product can be a growth media alone or modular greenroof products. In addition, the recycled super absorbent polymers can beused as a growth medium additive.

Other applications involving growth media are contemplated andconsidered within the scope. For example, it can be used as indoor andoutdoor potting soil, greenhouse and nursery soils, and additives forgeneral gardening. Entry into the modular greenroofing market lendsitself easily to window garden modules, living walls and other pottededible plants for people with limited space and no garden access aswell.

Soiled baby diapers collected in diaper bags are first sanitized usingsodium hypochlorite solution (bleach) and cleaning. Baby feces and otherhuman waste are separated from the diapers during this process. Afterinitial cleaning and sanitation, diapers, plastic bags and wipes arethen shredded allowed to settle down in water. Salts of different typeare added to adjust the separation power of water. Due to theirdifferences in density compared to water, these materials settle down astwo layers. The top layer, which has lower density than water, is mainlythermoplastics, such as polyolefins (polyethylene or polypropylenefibers or strips), polyester nonwoven mats, elastomers etc. The bottomlayer, which is heavier than water, is mainly soaked SAP and cellulosefibers and partially polyesters. The separation efficiency by thismethod is very limited. Therefore the purity of each separated portionis too low for other uses of them. Advantageously, the application doesnot require high purity materials. A small fraction of virgin plasticresins or other higher purity recycled materials may be used to improvethe waterproof performance if required.

After this partial separation of different diaper components, thepolyolefin portion will be compression-molded into square pans at hightemperatures (above the melting temperatures of polyolefins) as shown inFIG. 1. These pans are to hold growth medium, provide a waterproof orwater permeable bottom layer (7) and 4 side walls (5) and support theweight of the whole module. During the compression molding, snap-fitinterlocking structures are incorporated. Two tongues (3 and 8) andgrooves (4) of the snap fit interlocking structure are molded on to eachpan. Adhesives (6) can be applied inside the groove to permanentlyconnect adjacent trays together.

After the pans are manufactured, growth medium (1) are placed inside thepan. Growth medium can be in wet state, as one component of the growth,recovered SAP are in wet state. The growth medium includes recovered SAPand light weight soil. Lightweight soil is made of 22.74 vol % expandedclay (Miracle-Gro® prelate), 68.22 vol % peat moss (Miracle-Gro® peatmoss) and 9.04 vol % water. Other light weight soils may be used. FIGS.5 and 6 show the relationship between the composition of growth mediumand the water retention with or without nonwoven covers (2). Degree ofwater loss decreases with the increase of SAP content. The 30% waterretention time is almost double with SAP content range from 0% to 100%.Therefore, their drought resistance performance can be dramaticallydifferent. To test their drought resistant performances, 400 Penkoted®grass seeds or 25 transplanted grasses were planted in the above growthmedia in containers of 20 cm×20 cm×4.5 cm dimensions. After one monthwith little irrigation, only the grass in the containers with 75%SAP/25% soil and 50% SAP/50% soil in volume was observed alive. Finetuning tests have been carried out by applying 400 Penkoted grass seedsinto the same size container in order to determine the optimum contentof out growth medium. The results indicated 65% SAP/35% soil is theoptimum content of our growth medium. Examples 1 and 2 illustrate thegrowth medium performance.

Woven or nonwoven fabrics that can be polyester, polypropylene or nylonare welded onto the top of pans. The nonwoven or woven fabrics arespecially chosen so that their pores are large enough for plants, suchas grass grows through. The water retention time by using nonwoven/wovenfabrics cover can be up to 70% longer and more than those without suchkind of cover. This range includes all values and subrangestherebetween, including up to 10, 20, 30, 40, 50, 60, and 70% andlonger.

In the case that water is present in the shredded mixture ofthermoplastics and superabsorbent polymer particles, the first saltsolution may be obtained by adding solid salt to the shredded mixture,optionally with stirring. Water may be leftover in the shredded mixturefrom the sanitizing step, it may be added after the sanitizing step, orit may be leftover after rinsing the sanitized diaper components, or itmay be added after a rinsing step, or any combination of two or morethereof. Alternatively, the first salt solution may be first preparedfrom water and the salt, and then this solution is contacted with theshredded mixture. Alternatively, the first salt solution may be obtainedwith a combination of addition of sold salt to the shredded mixture andaddition of salt solution to the shredded mixture. In one embodiment,the salt or salt solution is contacted with the shredded mixture and isaccompanied by stirring or agitation or both.

In one embodiment, an amount of solid salt is added to the shreddedmixture to form the first salt solution and effect separation of theupper and lower layers. In one embodiment, a sufficient amount of saltsolution is added to the shredded mixture to form the first saltsolution and effect separation of the upper and lower layers. In oneembodiment, the salt solution is the first salt solution. In anotherembodiment, the first salt solution is formed at the time of adding saltor salt solution to the shredded mixture. In one embodiment, theconcentration of the salt solution is not particularly limited, and maysuitably range from greater than 1 to 70% by weight. This range includesall values and subranges therebetween, including greater than 1, 2, 3,4, 5, 6, 7, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, and 70%salt by weight, based on the total weight of salt solution. In oneembodiment, the concentration of the first salt solution is notparticularly limited, and may suitably range from greater than 1 to 70%by weight. This range includes all values and subranges therebetween,including greater than 1, 2, 3, 4, 5, 6, 7, 8, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, and 70% salt by weight, based on the totalweight of first salt solution. In one embodiment, the concentration ofthe salt solution or first salt solution is about 10% by weight based onthe total weight of the solution.

During the separation of diaper components, a certain water solutions ofsodium chloride, potassium chloride, sodium carbonate, potassiumcarbonate, calcium chloride, calcium sulfate, or mixture of two or moreof them are added into the separation medium to adjust the separationpower. The separation power of water is adjusted by addition ofinorganic salts in that salts will reduce the water uptake of SAPparticles. If salts are not added, SAP particles are swelled at theirmaximum, which lowers their density resulting in poor separation. Watersoluble calcium solutions are added to adjust the gel strength of SAP byforming calcium polyacrylate outside of the SAP particles (Scheme 1).Calcium polyacrylate is not a superabsorbent polymer; therefore itbehaves as a physical crosslinker when they occur in or outside of theSAP particles. The ratio of water soluble calcium (in the equivalent tocalcium chloride) to dry SAP should be maintained at lower than 3:10 bymass. Higher calcium amount can crash SAP particles and produce anon-superabsorbent polymer, which was used as a process to remove SAPfrom the desired pulp products in the diaper recycling pilot plant byProcter & Gamble and the Seattle Solid Waste Utility and RabancoRecycling Company in Seattle Wash. In one embodiment, the crashed SAPmay be subjected to a further recovery procedure to replace calciumcations with either sodium or potassium. Examples 3 and 4 provideprocedures and recipes for separation of diaper components as well asSAP recovery using dilute sodium or potassium chloride solution asseparation medium. Example 5 provides a procedure and recipe forseparation of diaper components as well as SAP recovery andreinforcement using dilute calcium chloride solution as separationmedium. Example 6 describes how to recover calcium crashed SAP using awater soluble carbonate salt.

Higher calcium concentration in the separation medium or in subsequenttreatments may be desirable only when SAP is very hard to separate fromthe rest of the materials. The complexity of the materials used in adiaper, together with the number of different manufacturers and brands,can lead to situations where two or more different materials are weldedtogether and their densities are in the similar range of swelled SAPparticles. A calcium concentration at which calcium to SAP weight ratiois 1:1 can reduce the swell ratio of SAP to less than 3 times of SAP'sown weight. Sodium or potassium carbonate can be used to recover calciumcrashed SAPs. The reaction is shown in Scheme 2. Example 5 and 6 providea procedure and two recipes for SAP recovery after crashed by highcalcium solutions.

Thermoplastic polymers are made up a big fraction of materials in adisposable diaper. These materials include polyethylene, polypropylene,and elastomer. All of these materials has a specific gravity less than1, which allows them float in water separation medium. A simple wetseparation process can produce thermoplastics and SAP particles. Awetlay process (U.S. Pat. No. 5,409,573) that is similar to paper makingprocess can be used to lay each of the component onto a conveyer beltand dry separately for later molding process. SAP can also be maintainedin wet state till the last step of green roof module assemblingprocedure.

Due to the mixture nature of the recovered thermoplastics, whichcontains polyethylenes, polypropylenes, polyesters, polyacrylics,elastomers and cellulose fibers, direct molding of this mixture wouldlead to modules with poor mechanical properties. A compounding processusing twin-screw extrusion method can mix these components up to producea polymer blend with much improved mechanical properties. Example 7 and8 discusses these two situations where the strength and elongation atbreak of the compressed sheet are dramatically different.

One embodiment relates to using recycled diaper materials to produce asuper drought resistant and lightweight green roof module product. Theinventors have found similarities in green roof materials and disposablediapers. The different components disposable diapers have been separatedwith simple, economical and environmentally benign manufacturing andprocessing. The separated materials were used to form different parts ofgreen roof modules. The thermoplastic materials in a disposable diapermay be reprocessed into the green roof tray, while the super absorbentparticles may be combined with other growth media into novel high waterretention growth media. The high water absorbance feature of disposablediapers is converted into the drought resistant feature of green roofproducts. The lower densities of thermoplastics and super absorbentmaterials compared to gravel and regular soil is transformed into thelightweight feature of the proposed green roof module.

One key procedure during this recycling process is the separation ofdifferent diaper components. Based on their relative densities in water,the components in a diaper can be roughly separated into two categories:those float (polyolefins) and those sink (superabsorbent, pulp and smallquantity of polyester nonwoven). The inventors have found that wetlaytechnology, such as used in paper-making processes may be used for boththe separation and the consequent mat formation using water with orwithout other additives as the separation medium. Both the proposedproduct (high tolerance to material purity) and the recycling andprocessing procedures preclude the strict requirements of traditionallengthy and costly recycling processes, for which high purity componentsare the target product.

One embodiment provides a growth medium containing superabsorbentmaterials, which can absorb much more water than commercially availablegrowth media. The water uptaking ability can greatly reduce irrigationso to provide a drought resistant feature. Given a certain growth mediumdepth, the growth media may contain 20% more water while its totalweight can be reduced by 20% comparing current products on the market.The present study also shows the feasibility to perform 100% recyclingof disposed diapers using the proposed economical recycling andmanufacturing processes.

It has now been found that the rate of relative water loss decreaseswith the increase of content of superabsorbent polymers. The waterretention time (at 70% water loss) is almost double with SAP contentrange from 0% to 100% as shown in FIG. 2. In this test, SAP refers tothe water absorbent materials recovered from diapers that includesuperabsorbent polymer particles and cellulose fibers.

The use of nonwoven cover provides an enclosure of growth medium duringthe shipping and installation. It also allows plants to grow through thepores, prolongs water retention time of growth medium, and preventserosion. The results also indicate that the water retention time withthis non-woven mat is 70% longer than that without the mat, as shown inFIG. 3.

In one embodiment, the growth medium compositions, considering growthand drought resistance, is about from 40-75% of wet SAP weight. Thebalancing components can be commercially available growth media.However, in one embodiment, iron containing soil may be avoided. FIG. 8shows comparison of the vegetation establishment in different growthmedium compositions with or without nonwoven covers.

The results also show that the saturated growth media contained 20% morewater content but 20% weight lighter compared other commercially growthmedia for a given green roof growth media depth, which determines whatand how plants grow. This feature, together with the drought resistantand lightweight features provide flexibility for architecture design,vegetation selection and maintenance.

One embodiment provides a recycling procedure to separate, recover andreinforce superabsorbent polymers (SAP) from recycled disposablediapers. Several inorganic salts can be added to the separation mediumand this treatment reinforces SAP by making a physically crosslinkednetwork in addition to the build-in chemical network in SAP particles(Schemes 1). This degree of the crosslinked network can be adjustedusing a recovery reaction based on water absorbance design requirements(Scheme 2). The advantages of this procedure are (1) dramaticallyincreasing the efficiency for separation of disposable diapercomponents; (2) retardation of SAP degradation in growth medium andavoiding the potential contamination to substantial environment.

In one embodiment, thermoplastic materials may be recovered fromdisposable diapers using wetlay process, a compounding procedure forhomogenize the recovered materials, and a optionally compression moldingprocedure to make green roof trays or other engineering materials. FIG.9 shows pictures taken during separation and wetlay processes indicatingthe separation of different diaper components in separation medium.

In one embodiment, a refining process may be used in addition to thewetlay process. This refining procedure allows formation of a uniform,high strength, clean, and easy-handling mat. FIG. 10 shows a comparisonof the nonwoven mat prepared with and without refining procedure.

It has now been found that soluble SAP can cause high amount of totalorganic carbon (TOC) content in degradation tests. A treatment procedurewas developed to lower TOC to undetectable level by using an economicalprecipitation agent. (FIG. 11)

One embodiment provides a procedure for cleaning and sanitation of dirtydisposable diapers. Preliminary microbiology test has shown thatbacteria can be completely killed following this process. Table 1 showsthe microbiological test results.

TABLE 1 Microbiology Tests results Bleach solution with Total 6% sodiumColiform, Water hypochlorite, MPN/ Sample Comments for Sample Collectionml 100 ml Water with 2 dirty diapers placed in trash can at 0 >2419.6dirty diapers ambient conditions for 1 week and soaked in then soakedinto 20 L water Water after Add 50 ml bleach solution, stir and 50 11.01^(st) addition wait 30 mm before water sample of bleach collection.Water after Add 50 ml more bleach, stir and wait 100 2 2^(nd) addition30 mm before water sample of bleach collection. Water after Add 50 mlmore bleach, stir and wait 150 <1 3^(rd) addition 30 mm before watersample of bleach collection.

Pre-customer disposable diapers were ground by using wood chippershredder, which was originally designed process. However the workingmechanism of this type of machine is not suitable for handling softmaterials like disposable diapers. The machine clogged very often andthe shredded parts did not meet the requirement for an efficientseparation in water. A commercial grade paper shredder machine, equippedwith twin-shaft grinding gears was then used for this task. Althoughmultiple passes have to be done to obtain small pellet sizes (˜5 mm inlinear dimension), the resulted shreds were acceptable for separation bywet method. A parallel attempt was also made to grind the diapers intofiner particles by using a plastics grinder at Akron University. Thesefine particles (˜1 mm in linear dimension), however, did not allowefficient separation in water or the other separation media. The reasonfor the separation dependence on particle size is unknown at thismoment. But further study and optimization is required for betterseparation.

By using pure water as the separation medium, visual separation can beseen as shown in FIG. 9a . But the separation efficiency is very lowbecause the SAP particles are highly swelled and occupying much of thevolume in the vessel. The viscosity of water appeared to be high aswell. Also due to the high swell ratio of SAP particles, their densitiesare essentially same as water. This problem is addressed by using saltsolutions.

Only two layers of the three layers settlement were seen becausepolyester nonwoven cannot differentiate from SAP particles in density.The reasons are that polyester nonwoven has high porosity, in which SAPparticles may present and they were treated for hydrophilicity also. Butsince polyester nonwoven are minor components, it was not furtherseparated. Therefore the polyolefins and the rest can be separated verywell, especially in salt solutions.

It is conventionally considered that disposable diapers contain 7% ofpolyester nonwoven fabric. However, it has now been found that this isonly qualitatively correct for some brands of diapers. Therefore, in oneembodiment, polyester nonwoven is not recovered as a separate component.

As mentioned above, the separation efficiency of pure water was verypoor. In addition it took a long time and large quantity of water toseparate very small amount of diaper components. To solve this problem,the swelled volume of SAP particles must be reduced, i.e., the densitymay be increased.

Aqueous solutions of sodium chloride, potassium chloride, sodiumcarbonate, potassium carbonate, calcium chloride, calcium sulfate, ormixture of two or more of them are added into the separation medium toadjust the separation power. The separation power of water is adjustedby addition of certain amount of inorganic salts in that salts willreduce the water uptake of SAP particles. If salts are not added, SAPparticles are swelled at their maximum, which lowers their densityresulting in poor separation. When water soluble calcium salts areadded, a calcium polyacrylate salt is formed (Scheme 1), which is not asuperabsorbent polymer and does not swell in water. This originallythought unsuitable reaction was used to form a chemically crosslinkednetwork in the SAP particles. By controlling the percentage of thisnetwork, the gel strength as well as the water uptaking capacity of SAPparticles can be adjusted. This reaction can also be used to sequesterwater soluble portion of SAP, which may otherwise increase total organiccarbon content in the waste water stream and the runoff water from thegreen roofs.

In one embodiment, a wetlay process may be used for one or bothseparation and sequential mat formation. A wetlay trial run wassuccessful. In one embodiment, a simple system with the most basiccomponents of a wetlay process may be used to separate and cleanmaterials. In carrying out or optimizing the process, one may considersolid/water ratio, salt concentration, agitation intensity, amount ofreusable separation medium (salt water), overall water usage, and dryingtime for wetlaid mat. Non-limiting examples of wetlay processes may befound at U.S. Pat. No. 5,409,573, issued Apr. 25, 1995 and “Bamboo FiberReinforced Eco-Composites by Wetlay Processing” Zhang, Wei, et al.,ANTEC 2007, pp. 2260-65, the relevant contents of each of which beinghereby incorporated by reference.

During the wetlay runs, it was found that the mat formed fromthermoplastic materials is loose and without strength. Even extreme carewas taken when handling, it still intended to break into parts, as shownin FIG. 10. It was also noticed that there is no binding between thelarge pieces of the thermoplastics, which prevents the formation auniform and self-supporting mat. Therefore, a refining process was addedprior to the actual wetlay mat formation. The refining processredistributes the pulp fibers in the medium and they behave as bindersin the mat. The resulting mat is shown in FIG. 10 in comparison with amat formed without refining. In addition to the usage in tray and panelforming via compression molding, the resulting coherent andself-supporting mat can also be a product by itself for applicationssuch as filter, ground cover, erosion control mat, tree protection mat,weed mat etc.

A degradation problem with superabsorbent polymers was observed duringgrowth media test. In the presence of rust (iron oxides) or any watersoluble iron ions, superabsorbent polymers will lose its water absorbingcapability. Iron can be a catalyst for degradation of superabsorbentpolymers or simply crash them like calcium salts. As such, in oneembodiment, it may be desirable to avoid iron in growth media as well asthe container.

It is feasible to produce the proposed novel modular green roof productfrom recycled disposable diapers and it has many advantages over theproducts on the current market. The most unique features are superdrought resistance and lightweight. Other associated features includereduced solid waste, better stormwater management, more energy saving,more beautiful landscaping, less pollution, etc.

The proposed manufacturing process, wet method separation and wetlayformation has been designed and initial trial runs with batch equipmenthave been finished. The results show that it is effective way to recycledisposable diapers with some modifications and continuous processes.This process and the product design allows 100% recycling of disposablediapers with different components converted to respective parts in amodular green roof product.

Vegetation development in this growth media was evaluated using aprototype green roof module. Within the limited study period, healthyplant growths are observed in growth media with 40-75% percent ofrecycled super absorbent polymers. Accelerated degradation studies underheat and UV irradiation showed relatively high TOC content in collectedwater sample. But it can be significantly lowered with simple treatment.Thermal and irradiation induced degradation may affect the life time ofthe growth media. A preliminary sanitation process was prepared andfollowed to clean dirty diapers. Common disinfection agent such asbleach at relatively low concentration performed satisfactory work inthis study.

Example 1. Vegetation Establishment from Seeds in Growth Media

The growth media includes recovered SAP and light weight soil withseveral compositions. Lightweight soil is made of 22.74 vol % expandedclay (Miracle-Gro® prelate), 68.22 vol % peat moss (Miracle-Gro® peatmoss) and 9.04 vol % water. The growth media compositions are: 100%SAP/0% soil, 75% SAP/25% soil, 50% SAP/50% soil, 25% SAP/75% soil and 0%SAP/100% soil by mass in wet state. The wet state means the maximumcapacity of water holdup without free flowing water. These growth mediawere placed in containers of dimension with 20 cm×20 cm×4.5 cm. In eachcontainer, 400 Penkoted® grass seeds were planted in growth media at 5mm deep. All these containers were placed in a simulated full sunenvironment at 24 hour per day. To maintain a healthy sprouting andgrowth of grass, extra water is provided during testing period. Theextra water was provided so that no free water can be observed at anytime. Because only a small amount of extra water was irrigated at arounda week interval, the grasses in the growth media were exposed to asimulated drought condition.

The grass was sprouting and growing much less in the container with 100%SAP because of poor air permeability and poor root development. Thesparsely sprouted grasses in this container died after two weeks. Thegrasses in the containers with 25% and 0% SAP initially sprout similarlywith other two containers with 75% and 50% SAP. However, the growth ofgrasses in the former two containers eventually became slow and died infour weeks. In contrast, the two containers with 75% and 50% SAP wereable to keep the grasses alive till 45 days and they can survive inanother two weeks after watering. The total amount of extra water isabout 3000 ml.

Example 2. Vegetation from Seeds in Growth Media with Nonwoven Cover

The growth media includes recovered SAP and light weight soil withseveral compositions. Lightweight soil is made of 22.74 vol % expandedclay (Miracle-Gro® prelate), 68.22 vol % peat moss (Miracle-Gro® peatmoss) and 9.04 vol % water. The growth media compositions are: 100%SAP/0% soil, 75% SAP/25% soil, 50% SAP/50% soil, 25% SAP/75% soil and 0%SAP/100% soil by mass in wet state. The wet state means the maximumcapacity of water holdup without free flowing water. These growth mediawere placed in containers of dimension with 20 cm×20 cm×4.5 cm. In eachcontainer, 400 Penkoted® grass seeds were planted in growth media at 5mm deep. A nonwoven fabric is placed on top of the growth medium in eachcontainer. The nonwoven fabric is specially chosen so that the pore sizeis large enough for grass sprouts to grow through. All these containerswere placed in a simulated full sun environment at 24 hour per day. Tomaintain a healthy sprouting and growth of grass, extra is providedduring testing period. The extra water was provided so that no freewater can be observed at any time. Because only a small amount of extrawater was irrigated at around a week interval, the grasses in the growthmedia were exposed to a simulated drought condition.

The grass was sprouting and growing much less in the container with 100%SAP because of poor air permeability and poor root development. Thesparsely sprouted grasses in this container died after two weeks. Thegrasses in the containers with 25% and 0% SAP initially sprout similarlywith other two containers with 75% and 50% SAP. However, the growth ofgrasses in the former two containers eventually became slow and diedfive weeks after watering stopped. 45 days and they can survive inanother two weeks after watering. However, the total extra water amountis only about 1800 ml. This result indicated that applying non-wovencover on the top of growth media can dramatically decrease the waterusage while still allow grass to survive a longer time during a droughtcondition.

Example 3. Use Dilute Sodium Chloride Solution as Separation Medium toSeparate Diaper Components

In a 1000 ml Flask, 15 gram of shredded diaper components were addedfirstly, then 1000 ml tap water was also added. The mixture was stirredand allowed for settle down for 15 minutes. After 15 minutes, however,it was hard to stir this mixture and there was no free water flowing inthe flask. All the components in the flask all gel up because the SAPabsorbs water and swell to much larger particles. However, by adding 5gram sodium chloride into the flask, which make the total concentrationof sodium chloride to 0.5% wt, the SAP particles shrunk to less than 50%of the size before sodium chloride is added. Hence, the mixtureparticles became easier to be stirred and free flowing. After furtherstirring and settle down, the majority of polyolefins such aspolyethylenes and polyproplylene float to the top of the flask, whileSAP and sink down to the bottom of the flask. A separation can be madeby removing the upper layer with most polyolefins and removing the lowerlayer with most SAP particles.

The efficiency of separation by a single settle down is not enough toremove SAP from thermoplastics. This is suggested by the water absorbingof the compression molded panels from the thermoplastics. So two moreseparations can be used to achieve higher purity of the polyolefins. Therecovered thermoplastics is 10 gram and the recovered SAP is 250 gram inwet state, which is 5 gram after dried.

In a 5 gallon container, 8 liter tap water with 40 gram sodium chloridewas used to separate 120 grams of shredded diaper components. After thelower layer where swelled SAP were removed, the solution was reused toseparate the SAP in the thermoplastics that was recovered from the upperlayer. This procedure was repeated for a total of three times. 80 gramsof thermoplastics were recovered and 40 gram dried SAP was recovered.Finally 1000 L water was used to rinse the thermoplastics, which in turncan be reused for future separation.

Example 4. Use Dilute Potassium Chloride Solution as Separation Mediumto Separate Diaper Component

In a 1000 ml Flask, 15 gram of shredded diaper components were addedfirstly, then 1000 ml tap water was also added. The mixture was stirredand allowed for settle down for 15 minutes. After 15 minutes, however,it was hard to stir this mixture and there was no free water flowing inthe flask. All the components in the flask all gel up because the SAPabsorbs water and swell to much larger particles. However, by adding 5gram potassium chloride into the flask, which make the totalconcentration of potassium chloride to 0.5% wt, the SAP particles shrunkto less than 50% of the size before potassium chloride is added. Hence,the mixture particles became easier to be stirred and free flowing.After further stirring and settle down, the majority of polyolefins suchas polyethylenes and polyproplylene float to the top of the flask, whileSAP and sink down to the bottom of the flask. A separation can be madeby removing the upper layer with most polyolefins and removing the lowerlayer with most SAP particles.

The efficiency of separation by a single settle down is not enough toremove SAP from thermoplastics. This is suggested by the water absorbingof the compression molded panels from the thermoplastics. So two moreseparations can be used to achieve higher purity of the polyolefins.

In a 5 gallon container, 8 liter tap water with 40 gram potassiumchloride was used to separate 120 grams of shredded diaper components.After the lower layer where swelled SAP was removed, the solution wasreused to separate the SAP in the thermoplastics that was recovered fromthe upper layer. This procedure was repeated for a total of three times.80 grams of thermoplastics were recovered and 40 gram dried SAP wasrecovered. Finally 1000 L water was used to rinse the thermoplastics,which in turn can be reused for future separation.

Example 5. Use Calcium Chloride Dilute Solution as Separation Medium toSeparate Diaper Components and Sap Recovery and Reinforcement

In a 1000 ml Flask, 15 gram of shredded diaper components were addedfirstly, then 1000 ml tap water was also added. The mixture was stirredand allowed for settle down for 15 minutes. After 15 minutes, however,it was hard to stir this mixture and there was no free water flowing inthe flask. All the components in the flask all gel up because the SAPabsorbs water and swells into much larger particles. However, by adding5 gram calcium chloride into the flask, which makes the totalconcentration of calcium chloride to 0.5% wt, the solution became cloudyand SAP agglomerated to small particles at the bottom. The volume of SAPparticles shrunk to less than 200 ml. Hence, the mixture particlesbecame easier to be stirred and free flowing. After further stirring andsettle down, the majority of polyolefins such as polyethylenes andpolyproplylene float to the top of the flask, while SAP and sink down tothe bottom of the flask. A separation can be made by removing the upperlayer with most polyolefins and removing the lower layer with most SAPparticles. The thermoplastics collected after two separations by reusingthe water solution are free of SAP and suitable for later processes.

The recovered SAP, unlike those recovered from sodium and potassiumchloride solutions, is white particles with smaller particle sizes.However, the strength of the particles appears to be stronger.

However, if the concentration of calcium chloride is tripled, the SAPparticles would shrink to minimal volume (less than 50 ml). And theseparation efficiency is highly improved. The thermoplastics collectedare free of SAP after just a single separation. However, the waterabsorption capacity of SAP is also lost and therefore the resulting SAPis useless in the current application where water absorption iscritical. In this case, the collected SAP is referred to as “crashedSAP”.

Example 6. Use Potassium Carbonate to Recover Calcium Crashed Sap

Crashed SAP small particles by calcium chloride solution in Example 8were placed back into a 1 L flask with 500 ml water. 500 ml solution ofpotassium carbonate (3 grams) was added into the flask. The mixture wasstirred allow settle down. After 4 hours, the crashed SAP smallparticles were observed to grow into larger particles. Eventually thetotal volume of SAP was recovered back to the 300 ml after overnightsoaking. The surface water was filtered out and SAP small particles wererinsed by water for 3 times.

Example 7. Use Sodium Carbonate to Recover Calcium Crashed Sap

Crashed SAP small particles by calcium chloride solution in Example 8were placed back into a 1 L flask with 500 ml water. 500 ml solutions ofsodium carbonate (3 grams) were added into the flask. The mixture wasstirred allow settle down. After 4 hours, the crashed SAP smallparticles were observed to grow into larger particles. Eventually thetotal volume of SAP was recovered back to the 300 ml after overnightsoaking. The surface water was filtered out and SAP small particles wererinsed by water for 3 times.

Example 8. Compression Molding of Separated Diaper Components and theirMechanical Properties

The thermoplastics recovered from the upper layer of shredded diapercomponent were melt-pressed to make panels by using a hot press machine.Hot press machine was preheated to 400 F for about 20 mins. Thethermoplastics strips and particles were placed between two stainlesssteel foil and covered by another two stainless steel plates, which arethen placed in between two hot plates. Wait for 15 minutes afterapplying gentle pressure. Then use an approximate pressure of 5 ton/ft²and degassing by 3 times bump cycles to remove air bubbles in the plate.The films were then cooled down to room temperature in the air. Tensiletests indicated the strength is 8 MPa and the strain at break is lessthan 8%.

Both the tensile strength and elongation at break are considered as lowfor polyolefin materials and it will not be suitable for the intendedapplications. The fractured surfaces of these specimens were examinedand it was concluded that the poor homogeneity and bonding of thethermoplastics strips and particles is the reason. The failure during atensile test is usually due to the poor bonding between differentmaterials in the specimen. So the materials must be homogenized toachieve better mechanical properties. A compounding process isincorporated to improve the mechanical properties as discussed inExample 11.

Example 9. Compounding and then Compression Molding of Separated DiaperComponents and their Mechanical Properties

In a preheated (210° C.) mixing bowl of a Brabender Plasticorder blender(Model: S650-M, Brabender), 200 grams of the recovered thermoplasticswas added. Wait for 15 minutes for the plastics to soften or melt. Theblender is then turned on to median speed for 20 minutes. Stop theblender and collect the blended materials. Use the same compressionmolding process described in Example 10 to press films and cut tensiletest coupons, The tensile strength is found to be 11 MPa and the strainat break is found to be 14%.

Plastic compounding was carried in a sigma blender without inert gasprotection. To avoid excessive oxidation to the materials, rather lowmixing temperatures were used. Meanwhile, the mixing machine is batchmixer with limited shear stress capability. These factors caused limitedmixing efficiency. An industrial version of mixer, twin-screw extrudermay improve mixing efficiency and prevent oxidation with enclosed barreland inert gas protection.

In one embodiment, a weed control and moisture conservation mat (“WCMC”)is provided. In one embodiment, the mat is not intended to interferewith the root system like the agriculture applications of superabsorbent polymers but rather the mat is used to hold large quantity ofwater above the root system. The water absorbed by SAP can seep intosoil and maintain a high moisture atmosphere to slow down the moistureloss from soil.

The mat may be suitably used at any stage of the tree's growth, fromseedling, to young tree, to a mature tree. In one embodiment, the matmay be used on a young tree or mature tree. In another embodiment, themat may be used on a mature tree, and not on young tree or seedling.

Wetlay is a modified paper-making process for nonwoven materialsmanufactured from fiber-like raw materials. In the wetlay process, asillustrated in FIG. 13, fibers are mechanically dispersed in an aqueousslurry solution (whitewater). The agitation of the mixture creates aslurry that is dewatered under vacuum as it is cast onto a moving,forming wire conveyor to form a continuous, non-woven, intermingled matof the fibers. Whitewater filtrate is recycled and returned as dilutionwater. The resulting mat is subsequently fed into a convectivethrough-air oven where it is dried and fused into a coherent, flexible,and highly porous mat. The resulting mat is then used either as thefinal product or as a feedstock for subsequent material processing. Theresult of this technology yields a competitive and cost-effective venuewith minimal environmental impact to produce novel materials.

Commercial weed mats suppress weed growth by eliminating their contactwith air and light. Preservation of moisture is achieved by slow downevaporation. These two aspects can be utilized in the design of theproposed product with a top non-permeable layer. In one embodiment, anextra layer may be added that holds a large amount of water,water-holding layer. To slow down the releasing rate of water into soil,a semi-permeable layer can also be added. With the combination of anon-permeable top layer, a water-holding layer and a semi-permeablecontrol layer, the mat can achieve the goals of weed control andmoisture conservation. To allow rain water seep into the water-holdinglayer, seep holes or channels can be incorporated. FIG. 7 shows a modeldesign of this weed control and moisture conservation (WCMC) mat.

In one embodiment, the basic components of the proposed WCMC matincluding a waterproof top cover layer, a water-holding center layer anda semi-permeable base layer can be made from different parts of adisposable diaper. The waterproof top cover plate will be made of thepolyolefin components from the diaper. High temperature compressionmolding will be needed to re-melt and solidify into non-permeable hardplates. The water-holding center layer will be made from a mixture ofthe superabsorbent polymers, cellulose, polyester, and polyolefinfibers. These components can be loosely bonded together to allow maximumamount of water absorbing capacity. Slow-releasing fertilizers may alsobe incorporated in this layer if desired. A semi-permeable base layerwill be made of polyester nonwoven fibers. It will be welded onto thetop cover plate to form a pocket sandwiching the water-holding layer.The base layer will also act as a protection layer during shipping andhandling and as a moisture permeation regulation layer after installed.

Traditional efforts on recycling disposable diapers were not profitablebecause recycled materials with very high purity were targeted. The costfor obtaining high purity of recycled materials offsets all the possibleprofits in those developments. In contrast, high purity materials in thepresent application are not required. The only part that may needrelatively high purity polymers is the top cover plate, where waterproofis required. As a result, the overall equipment requirement forseparation is low. So will be the energy consumption and labor cost forthis process. Furthermore, a rough separation can be achieved based onlyon the densities of the diaper components relative to water. They can becategorized as: polyolefins (low density), water swelled superabsorbentand cellulose, and polyesters (high density). They will float, suspendor sink in water resulting in a partial separation.

In one embodiment, features such as controlled-release fertilizer may beused in the center layer or green roof.

FIG. 14 shows a schematic flow chart of the one embodiment of theproduction process and design of WCMC mat. First step involvescollection, cleaning and shredding the disposable diapers into shortfibers and strips. Because disposable diapers are made by more than 10different components, it is impossible to separate each individualcomponent completely. Fortunately, they can be roughly and partiallyseparated by their densities using water (specific gravity, SG=1) as theseparation medium. The present inventors have found that they can beseparated into two groups: heavier than water (SAP, polyester nonwovenand cellulose fibers) and lighter than water (majority is polyolefinmaterials). Their purities are poor and they are not suitable for otherusages. Advantageously, the proposed application does not require highpurity materials.

After this partial separation of different diaper components, thepolyolefin portion may be compression-molded into panels at hightemperatures (above the melting temperatures of polyolefins). A sampleis shown in FIG. 15a . These panels may be used as the top plate of themat as the waterproof and support for the whole mat. The intermediatedensity portion may be compressed and dried to form pads for the centerlayer of the mat. The presence of cellulose fibers and small amount ofpolyester nonwovens helps this process and a self supporting mat can bemade, FIG. 15b . The bottom layer of this design may be made from aporous and water permeable nonwoven or woven material. The porosity andthe hydrophobicity of this layer can be tuned to control thepermeability of water through this layer. After the individual layersare prepared, the WCMC mat can be assembled by compression molding orheat bonding around the edges.

It should be pointed out that the mechanical strength of the panels showin FIG. 15a is not very good due to poor mixing and adhesion ofdifferent components. But after further blending, the mechanicalstrength can be improved by at least 70%.

FIG. 12 shows a preliminary study on the effectiveness of the SAP onyoung tree protection after 5 months of usage. A simplified version ofprototype WCMC, mulch only and a commercial mat was compared in thisstudy. The average new growth of each branch, total length of newgrowth, total number of new branches were compared for three appletrees. It is clear that the WCMC mat is much better than the commercialweed mat and mulch only.

WCMC mat can offer fruit trees with sustained moisture around their rootsystems. If slow releasing fertilizer is incorporated, fertilizing andmoisture can be regulated together at a steady rate based on trees'need. With the high water-holding capacity and weed suppressantfunction, WCMC mat will reduce the number of irrigation so to lower thecosts on water, power, equipment, and labor. It will also reducedrought-related diseases and damages. With faster growth rate and highersurvival rate, young fruit trees can yield better-quality fruits andsooner than others. In addition, farmers can improve the soil quality ofwasteland and degraded soil areas by using the WCMC mat with regulatedfertilizing and moisture control. Therefore, farmers can plant fruittrees in area that usually not suitable for them. Arid/semiarid areascan also be transformed and improved so that they are suitable foragriculture usage.

Not only can WCMC mat be used for trees directly related to foodproduction, but this product can also be used to boost food productionby increasing the total forest coverage of the surrounding areas of afarm. With the improved environment and better local climate near farms,food production can be indirectly increased. For an example, trees canbe planted near farms as wind breakers to protect crops and reduce theloss of top soil. For another example, farms and orchards near a bigforest do not need worry about pollinators, which nest in theneighborhood forest. The humidity and air temperature can also beregulated by the nearby forests.

As one way to restore the functions of forests,afforestation/reforestation is of great importance. Therefore, WCMC matproduct will satisfy the public interest in that it can help treeprotection, improve the survival rate and growth rate of young trees,reduce damages and death during droughts, allow afforestation inarid/semiarid regions, and enable reforestation on degraded soil and inwasteland areas. The product can help to reduce water and energyconsumptions as well as lower labor and maintenance requirements ontrees' after-planting cares. In summary, the WCMC mat can help to“protect and enhance the national's forest resources and environment”.

One embodiment provides a light-weight, three-layer modular green rooftray. (1) The bottom layer as water-proof layer is made from recoveredthermoplastic materials from recycling disposable diapers; (2) Thecenter layer is a drought resistant growth medium containingsuperabsorbent polymers, and (3) The top layer is a porous nonwovencover.

In one embodiment, the modular green roof tray contains a snap-fitlocking mechanism. In one embodiment, the snap fit is a 3D lockingmechanism. In one embodiment, the snap fit includes an adhesive placedon the snap tongue portion. In one embodiment, the interlocked modularuses weight to hold on top of roof. In one embodiment, weight is notused to hold on top of roof.

In one embodiment, the cover of green roof tray may be made by lowdensity and large pore-sized nonwoven mat. In one embodiment, this coverperforms as an enclosure of growth medium during the shipping andinstallation, allows plants to grow through the pores, prolongs waterretention time of growth medium, and prevents erosion.

In one embodiment, the non-woven mat cover has 70% longer waterretention time for growth medium than that without the cover.

In one embodiment, the growth medium composition of green roof traycontains 90-20% SAP optimum at 65%.

In one embodiment, the SAP act as drought resistant component.

In one embodiment, the SAP is recycled and recovered from disposablediapers.

In one embodiment, when the growth medium composition is used as pottingsoil for indoor house plants such as Dwarf Umbrella tree (Scheffleraarboricola) and Kentia palm (Howea forsteriana), watering frequency canbe reduced down to once every 12 weeks.

In one embodiment, the growth medium composition is also applicable toone or more of non-modular green roof design, indoor house plants, otherhorticulture plants.

In one embodiment, the SAP may be recovered from disposable diaper asfollows:

-   i. Dilute calcium chloride solution. Ratio of CaCl₂ to dry SAP is    3:10. This not only can efficiently separate SAP from the rest of    the pulp, but also improves the gel strength. The mechanism for this    gel strength enhancement is that calcium polyacrylate behaves as a    physical crosslinker-   ii. In conventional systems, the SAP was not recovered. A much    higher concentration of calcium solution was used that results SAP    were all crashed out. This work is to use dilute calcium solution    and control the ratio of calcium and SAP.-   iii. Recovering crashed SAP due to high calcium concentration can be    done by applying solutions of potassium or sodium carbonate. Calcium    then reacts with carbonate to form calcium carbonate and release the    polyacrylate to reform sodium or potassium polyacrylate.

In one embodiment, the plastics or thermoplastics may be recovered fromdiaper materials using wet method.

In one embodiment, a compounding process may be applied to the plasticsrecovered from diaper.

In one embodiment, the tree protection mat has a water absorptioncapability such that it can slowly release water into soil.

One embodiment relates to a process for recycling soiled disposablediapers, comprising:

contacting a plurality of soiled disposable diapers with at least onebleaching agent to sanitize the diapers, to form a mixture comprisingsanitized diaper components;

shredding the sanitized diaper components, to form a shredded mixturecomprising thermoplastics and superabsorbent polymer particles;

contacting the shredded mixture with a first salt solution to increasethe density of the superabsorbent polymer particles and form adensity-separated mixture having an upper layer comprisingthermoplastics and a lower layer comprising superabsorbent polymerparticles and wastewater;

separating the upper layer from the lower layer, to obtain separatedthermoplastics and separated superabsorbent polymer particles;

compounding the separated thermoplastics in an extruder to form athermoplastic polymer blend; and

separating the separated superabsorbent polymer particles from thewastewater.

In one embodiment, the thermoplastics comprise one or more polyolefins.

In one embodiment, the thermoplastics are one or more polymers selectedfrom the group consisting of polyethylene, polypropylene, copolymer ofethylene and other alkene, HDPE, LDPE, copolymer of two or more thereof,and a combination of two or more thereof.

In one embodiment, the thermoplastics further comprise one or moreselected from the group consisting of polyester, polyacrylic, cellulose,elastomer, nylon fiber, polyethylene fiber, polypropylene fiber, and acombination of two or more thereof.

In one embodiment, the superabsorbent polymer particles comprisepolyacrylic acid polymer, polyacrylate polymer, starch-grafted polymer,polyacrylamide, ethylene maleic anhydride polymer,carboxymethylcellulose, polyvinyl alcohol, polyethylene oxide, starchgrafted copolymer of polyacrylonitrile, Group IA salts of polyacrylicacids, copolymer of two or more thereof, or a combination of two or morethereof.

In one embodiment, the superabsorbent polymer particles are crosslinked,linear, copolymeric, or a combination of two or more thereof.

In one embodiment, the bleaching agent is selected from the groupconsisting of sodium hypochlorite, potassium hypochlorite, chlorine,ozone, oxygen, calcium hypochlorite, hydrogen peroxide, chlorinedioxide, and a combination of two or more thereof.

In one embodiment, the bleaching agent is selected from the groupconsisting of sodium hypochlorite, potassium hypochlorite, and acombination thereof.

In one embodiment, the first salt solution is an aqueous solution of atleast one Group IA, IIA, IIIA, or VIIIA metal salt, or a combination oftwo or more thereof.

In one embodiment, the first salt solution is an aqueous solution of atleast one Group IIA or IIIA metal salt, or a combination thereof.

In one embodiment, the first salt solution is an aqueous solution of atleast one Group IIA metal salt, or a combination thereof.

In one embodiment, the first salt solution is an aqueous solution ofsodium chloride, potassium chloride, calcium chloride, sodium carbonate,potassium carbonate, calcium carbonate, sodium hydrogen carbonate,potassium hydrogen carbonate, sodium nitrate, potassium nitrate, calciumnitrate, sodium hypochlorite, potassium hypochlorite, calciumhypochlorite, aluminum salt, boron salt, iron salt, or a combination oftwo or more thereof.

In one embodiment, the first salt solution is an aqueous solution ofcalcium salt.

In one embodiment, the separated superabsorbent polymer particles arecontacted with a second salt solution to decrease the density of theseparated superabsorbent polymer particles, to form a mixture comprisingdecreased density superabsorbent polymer particles and a secondwastewater.

In one embodiment, the decreased density superabsorbent polymerparticles are separated from the second wastewater.

In one embodiment, the second salt solution is an aqueous solution of atleast one Group IA, IIA, or IIIA metal salt, or a combination of two ormore thereof.

In one embodiment, the second salt solution is an aqueous solution of atleast one Group IA or IIA metal salt, or a combination thereof.

In one embodiment, the second salt solution is an aqueous solution of atleast one Group IA metal salt, or a combination thereof.

In one embodiment, the second salt solution is an aqueous solution ofsodium chloride, potassium chloride, sodium carbonate, potassiumcarbonate, sodium sulfate, potassium sulfate, sodium nitrate, potassiumnitrate, or a combination of two or more thereof.

In one embodiment, the second salt solution is an aqueous solution of asodium salt, potassium salt, or a combination thereof.

In one embodiment, the upper and lower layers are separated byscreening, filtering, decanting, centrifuging, hydrocycloning, movingweb, or a combination of two or more thereof.

In one embodiment, the separated superabsorbent polymer particles aredried.

In one embodiment, the separated superabsorbent polymer particles arecontacted with soil, earth, mulch, peat moss, biomass, compost, topsoil,sand, organic plant growth material, nitrogen-containing fertilizer,phosphorus-containing fertilizer, lime, herbicide, potting soil, growthmedium, fertilizer, or a combination of two or more thereof, to form aplant growth medium.

One embodiment provides a plant growth medium, produced by the processdescribed herein.

One embodiment provides a process for growing plants, comprisingcontacting the plant growth medium with a plant or seed.

In one embodiment, the compounding is carried out in a batch process, acontinuous process, or a combination thereof.

In one embodiment, the extruder is a single screw or multi screwextruder, or a combination thereof.

In one embodiment, one or more of molding, extruding, thermoforming, orpelletizing the thermoplastic polymer blend, may be used to form aplastic article.

In one embodiment, molding is injection molding, compression molding,rotational molding, or a combination of two or more thereof.

In one embodiment, the thermoplastic polymer blend is contacted withepoxy; adhesive; virgin or recycled resin of one or more ofpolyethylene, polypropylene, polyester, or other thermoplastic; fiber,reinforcement fiber, glass fiber, carbon fiber, aramid fiber, woodfiber, plant fiber, cellulose, filler, clay, nanoclay, carbon black,carbon nanotube, glass bead, silica, titanium dioxide, calciumcarbonate, fire retardant, pigment, antioxidant, fragrance, or acombination of two or more thereof.

One embodiment provides a plastic article, produced by the processdescribed herein.

One embodiment provides a modular green roof tray, comprising:

a waterproof bottom layer made from a thermoplastic material;

a center layer disposed over the bottom layer and comprising a droughtresistant growth medium containing superabsorbent polymer particles; and

a porous nonwoven top cover disposed over the center layer.

In one embodiment, side walls made from the thermoplastic material areprovided, said walls surrounding side portions of the center layer.

In one embodiment, one or more of the side walls further comprise asnap-fit locking mechanism.

In one embodiment, the snap-fit locking mechanism are capable ofsnap-fitting and locking to one or more side walls of an adjacentmodular green roof tray.

In one embodiment, the porous nonwoven material is a low density andlarge pore-sized nonwoven mat.

In one embodiment, the growth medium comprises 90-20% by weight of thesuperabsorbent polymer particles.

In one embodiment, the growth medium comprises about 65% by weight ofthe superabsorbent polymer particles.

FIG. 12 graphically shows the effect of one embodiment of the treeprotection mat on the growth of three newly planted apple trees after 5months. In this figure a tree protection mat, hardwood mulch and acommercial weed mat made of recycled rubber strips that withoutsuperabsorbent polymer particles were compared. The average new growthof each branch, total length of new growth, and total number of newbranches were compared. It is clear that the tree protection mat is muchbetter than the commercial weed mat and hardwood mulch.

One embodiment provides a tree protection mat, comprising:

a top cover plate, comprising a waterproof material having holes thereinto permit water to flow therethrough;

a center layer disposed beneath the cover plate and comprisingsuperabsorbent polymer particles; and

a semipermeable bottom layer disposed beneath the center layer.

One embodiment provides a tree protection mat, comprising:

a top cover plate;

a center layer disposed beneath the cover plate and comprisingsuperabsorbent polymer particles; and

a semipermeable bottom layer disposed beneath the center layer;

wherein the top cover plate reduces or prevents evaporative water lossfrom the center layer.

The choice of material for the top cover plate is not particularlylimited, so long as it reduces or prevents evaporative water loss fromthe center layer. The top cover plate material may be made ofthermoplastic such as polyethylene or other plastic film or laminate;may be woven or nonwoven; it may be waterproof or semipermeable towater; it may be unperforated or perforated with holes or small funnels,for example of the type used in VISPORE™ Tree Mat materials; or anycombination thereof. In one embodiment, the top cover plate materialincludes one or more UV resistant additives, to resist against sundamage.

The top cover plate may be waterproof and prevent evaporative water lossfrom the center layer. It may also be semipermeable to water, and allowwater in the form of moisture, precipitation, or watering, to flowthrough to the center layer; or it may include an opening, such as ahose fitting, to allow connection to a water hose, and thereby water andoptionally growth media such as fertilizer can be pumped through thefitting and hydrate the center layer; or any combination thereof.

So long as it allows water to seep down into the ground from the centerlayer, the choice of material for the semipermeable bottom layer is notparticularly limiting. For example, it may be made of woven or nonwovenfabric, semipermeable material, natural or synthetic fiber, rayon,nylon, polyester, polyethylene, polypropylene, cotton, nylon, acrylic,or the like, or any combination thereof.

The top cover plate, center layer, and semipermeable bottom layer may besandwiched together, in the order prescribed herein, and optionallysealed at the perimeter edge by sewing, gluing, heat sealing, or thelike. Alternatively, it may include a sidewall, which extends around theperimeter, which sidewall may be waterproof or semipermeable to water.The sidewall may be connected to the top cover plate, center layer, andsemipermeable layer as appropriate. In either case, the mat may includean access slit and a hole in the center, such as shown in FIG. 7, toallow placement around the trunk or stem of the tree, shrub, bush,sapling, or other plant. The sides of the access slit may include ties,snaps, Velcro, zipper, or similar methods of connecting the two sides ofthe slit to one another. The mat may lay flat or it may have a built-inshape such as a cone or rounded shape, for example, to accommodate theground around the subject plant or to accommodate the shape of the plantitself.

In one embodiment, the top cover plate reduces evaporative water lossfrom the center layer. In another embodiment, the top cover plateprevents evaporative water loss from the center layer.

In one embodiment, dry SAP refers to SAP at standard temperature andpressure. In one embodiment, dry SAP contains about 10% by weight ofwater.

This application is based on and claims priority to U.S. ProvisionalApplication Ser. No. 61/538,565, filed Sep. 23, 2011, the entirecontents of which are hereby incorporated by reference, the same as ifset forth at length.

The invention claimed is:
 1. A tree or plant protection mat, forplacement on the ground around a trunk or stem of the tree or plant, toprotect said tree or plant, comprising: a top cover plate consisting ofwoven polypropylene fabric; a center layer disposed beneath the coverplate and comprising superabsorbent polymer particles, wherein thesuperabsorbent polymer particles comprise polyacrylic acid polymer,polyacrylate polymer, starch-grafted polymer, polyacrylamide, ethylenemaleic anhydride polymer, carboxymethylcellulose, polyvinyl alcohol,polyethylene oxide, starch grafted copolymer of polyacrylonitrile, GroupIA salts of polyacrylic acids, copolymer of two or more thereof, or anycombination thereof; and a semipermeable bottom layer disposed beneaththe center layer; wherein the top cover plate and semipermeable bottomlayer are sealed together at their perimeter edges by sewing, gluing,heat sealing, or any combination thereof, to sandwich the center layerbetween the top cover plate and semipermeable bottom layer; wherein thetop cover plate reduces or prevents evaporative water loss from thecenter layer; and wherein the semipermeable bottom layer permits waterto seep out from the center layer onto the ground, when the mat isplaced around a trunk or stem of the tree or plant.
 2. The mat of claim1, wherein the superabsorbent polymer particles are dry.
 3. The mat ofclaim 1, wherein the center layer further comprises one or morecellulose fibers, polyester fibers, and polyolefin fibers,controlled-release fertilizer, or any combination thereof.
 4. The mat ofclaim 1, wherein the semipermeable bottom layer comprises woven ornonwoven fabric, natural or synthetic fiber, rayon, nylon, polyester,polyethylene, polypropylene, cotton, acrylic, or any combinationthereof.
 5. The mat of claim 1, wherein the semipermeable bottom layercomprises nonwoven polyethylene fabric, nonwoven polypropylene fabric,or a combination thereof.
 6. The mat of claim 1, further comprising ahole through the top cover plate, center layer, and bottom layer, forthe tree or plant.
 7. The mat of claim 1, wherein the top cover platereduces evaporative water loss from the center layer.
 8. The mat ofclaim 1, wherein the top cover plate prevents evaporative water lossfrom the center layer.
 9. The mat of claim 1, further comprising a holeand an access slit through the top cover plate, center layer, and bottomlayer, for the tree or plant.
 10. The mat of claim 1, wherein the centerlayer further comprises cellulose fibers.
 11. The mat of claim 1,wherein the center layer further comprises polyester fibers.
 12. The matof claim 1, wherein the center layer further comprises polyolefinfibers.
 13. The mat of claim 1, wherein the center layer furthercomprises controlled-release fertilizer.
 14. The mat of claim 1, whereinthe semipermeable bottom layer comprises nonwoven polyethylene fabric.15. The mat of claim 1, wherein the semipermeable bottom layer comprisesnonwoven polypropylene fabric.
 16. A method for growing a tree or plant,comprising placing the mat of claim 1 around a trunk or stem of the treeor plant.
 17. A method for making the mat of claim 1, comprisingsandwiching the center layer between the top cover plate and thesemipermeable bottom layer and sealing the cover plate and semipermeablebottom layer together at their perimeter edges by sewing, gluing, heatsealing, or any combination thereof, to provide the mat.